Only two methods are available for an existing vacuum device to complete quenching. One is high-pressure gas quenching after heating, and the other is oil quenching at atmospheric or low pressure in a quenching chamber after heating.
The high-pressure gas quenching has advantages of reducing heat-treatment deformation of a part and avoiding pollution caused by oil quenching of a workpiece (the workpiece does not need to be cleaned after gas quenching), which is an oxidation-free and pollution-free heat treatment technology. However, it also has a significant disadvantage: Gas is used as a cooling medium, and has very limited thermal conductivity that is much lower than the thermal conductivity of a liquid. Therefore, to ensure the heat treatment effect of high-pressure gas quenching, only a small workpiece or a thin workpiece can be treated.
Liquid quenching has a good cooling speed, and basically can satisfy quenching processes of various workpieces. However, quenching deformation, cracking, and other heat treatment defects cannot be avoided, and steam produced during quenching pollutes a heating chamber to some extent, making it difficult to reach a vacuum degree that needs to be set. Therefore, the heating chamber and a workpiece transfer platform need to be cleaned regularly.